How to animate small water surfaces in structures?
Final:



You can fake it pretty easily with creative UV Mapping and animating Texture location. I've used Noise Texture for it as a Bump for Principled BSDF.

Let's break it down.

Mesh:

It's simple Plane with one edge Beveled. Nothing to add here.



Material:

We need to add material first, it will be easier during UV Mapping. 

Again, nothing to fancy here. 



Animating.

X value in Mapping node will be animated - in this example keyframes are on frame 1 with value 0 and on frame 60 with value 1. In your case axis could be different, also bigger difference between values will give faster animation.

After adding keyframes you should go to Dope Sheet editor, select both frames from X axis and choose Key > Interpolation Mode > Linear.

UV Mapping:

Go to Edit Mode, Select All and U > Unwrap.



Now changing X axis value in Mapping node should give as something like this (I'm using Node Wrangler to be able to see Color Ramp node output):



Go back to UV Image Editor, select faces where water should be flowing faster, enable Proportional Editing and scale them down along X axis as much as you want.



Final thoughts:

This is basic overview for the water flow. You should also add some Particle system for the splashing water and maybe some foam texture. I think those should be another questions otherwise this one could become to big/tutorial like answer. Or just search trough the web, there are plenty tutorials about this.